UL891 distribution panel

Switchgear and separately separated distribution panels require a rear channel for connecting incoming and outgoing feeder cables. However, prefabricated modular distribution panels are typically only used for front access of incoming and feeder cables. Therefore, distribution boards that are 45 inches deep or smaller can be placed against the wall. The maximum feeder that can be used for assembly is a 1200 ampere molded case circuit breaker. In the distribution panel where molded case circuit breakers are installed in groups, feeders with a rated current exceeding 1200 amperes will be installed separately. Generally speaking, switchgear and individually separated distribution panels occupy more space than distribution panels with group installation of molded case circuit breakers. Ferranti switchgear and separate distribution panels provide insulated and isolated busbar systems. This option can significantly reduce the chance of arcing faults occurring on the busbar or grounding, and should be considered when highly concerned about the safety of such faults. In UL1558 switchgear, all protective devices are withdrawable, installed separately, and separated separately. UL891 distribution panel protection components can be installed in groups or separated separately.

Separate distribution panels place each circuit breaker behind its own door and partition, isolating it from surrounding equipment; These are also identified as AV3 access and power interruption distribution panels. Some distribution boards may contain a combination of individually installed and grouped installed protective components. In these cases, devices installed separately are not separated separately. Here, we must investigate the level of selectivity between the required protective components. Low voltage molded case circuit breakers can be constructed without instantaneous tripping function. Both the main circuit breaker and the feeder circuit breaker are like this. If there is no instantaneous tripping function, the main equipment, feeder, and possibly other downstream equipment can coordinate more fully with each other. But in addition to the switchgear, there is a second option, the separate compartment distribution panel of Ferranti Electric also has a rated withstand voltage of 30 cycles and can withstand short-circuit currents.

Therefore, it is possible to affect a higher level of selectivity between LVPCBs in the switchgear or between LVPCBs separated from ICCBs or MCCBs in the distribution panel. Due to their short-circuit rating of 30 cycles, these distribution boards can still be listed in UL 891. On the other hand, the assembly of the distribution panel must use protective components that include instantaneous tripping function. In the presence of high current faults exceeding the instantaneous set point, the flexibility of the UL891 distribution panel has been improved to the level where bolt connections or plug-in structures can now be used.

In bolted connection design, protective components are securely bolted to the main distribution busbar. The plug-in structure includes a detachable module, on which protective components are installed and allow them to be clamped onto the main distribution bus. This connection is made using spring reinforced high-voltage clamps, designed to grip the busbar more tightly under high fault conditions. The main advantage of the plug-in structure is that the protective device can be quickly removed from the board without the need to unplug the circuit breaker (or switch) from the main busbar.

Although the main busbar needs to be disconnected for safety purposes, this feature can minimize the disconnection time to the greatest extent possible. It only increases the cost of the circuit board by about 2% and has no impact on the overall switchgear footprint. For applications with 1200A or lower, the main protective component can be installed separately or in combination with the feeder group. The first substation group includes a special case, situation 3A, to illustrate the possible consequences of this option. In this case, installing the host group only saved about 4% of the cost, but eliminated the entire cabinet stack, thereby reducing the footprint by 43%! The cable entry space is easy to install, the feeder section operates at low temperatures for a long time (which means it prolongs equipment life), and the power supply of the feeder section is completely isolated when the main power is turned on. For a cost increase of only 4%, these are significant benefits, but only if the footprint allows.